This really explains why we feel so bad during jet lag, or if we have to work irregular shiftsDr Simon Archer, University of Surrey

Blood tests showed that normally 6% of genes - the instructions contained in DNA - were precisely timed to be more or less active at specific times of the day.

Once the volunteers were working through the night, that genetic fine-tuning was lost.

Chrono-chaos

"Over 97% of rhythmic genes become out of sync with mistimed sleep and this really explains why we feel so bad during jet lag, or if we have to work irregular shifts," said Dr Simon Archer, one of the researchers at the University of Surrey.

Fellow researcher Prof Derk-Jan Dijk said every tissue in the body had its own daily rhythm, but with shifts that was lost with the heart running to a different time to the kidneys running to a different time to the brain.

He told the BBC: "It's chrono-chaos. It's like living in a house. There's a clock in every room in the house and in all of those rooms those clocks are now disrupted, which of course leads to chaos in the household."

Night shift tips from Twitter

Dave Tilley, who worked night shifts as a radio controller for an emergency doctor service, said: "I found the hardest part was a wall around 04:30. Strong coffee and Polo mints helped."

Wendy Smethurst, a doctor, said: "Have a dirty breakfast bap in the morning, sleeping tablet in the morning, shed loads of coffee, tea and chocolate. Also, getting to cuddle a new-born baby at 04:00 or see a baby born helps keep you awake."

Philippa Perry said: "When I was working at McDonald's I tried to mend a toaster at 07:00 after I had been on all night. Forgot to unplug it. Shock threw me across room. Don't tackle or mend electrical appliances when you're tired."